Drawing die



Jan. 23, 1934. A. P. ROUX 1,944,759

DRAWING DI E Original Filed Sept. 12, 1929 INVENTOR fiar/ofi P Pol/x M 752.7:

ATTORNEYS Patented Jan. 23, 1934 UNITED STATES PATENT OFFICE DRAWING DIE Adrian P. Roux, Oriskany, N. Y., assignor to General Cable Corporation, New York, N. Y., a corporation of New Jersey 8 Claims.

This invention relates to drawing dies and has for an object the provision of an improved die. This application is a division of my application, Serial Number 391,994, filed September 12th, 1929.

Although there is a constant search for substitutes for diamond dies, up to the present time none has been found which possesses all the desirable qualities of diamond. But diamonds are very expensive especially in larger sizes and are diificult to mount satisfactorily. They are also brittle and have other undesired characteristics. As will be disclosed hereinbelow I have provided a mounting for diamonds or other hard die cores which permits the use of very small sizes, and which furnishes so substantial a backing or matrix for them that their tendency to split is greatly reduced and they can be used until only a thin shell or ring remains.

It has been the practice to some extent to cast a body or matrix of iron, steel, bronze or other metal upon the diamond or other hard object as a core and then to pierce the blank thus formed through the hard core to form the die. But the matrix materials heretofore used or proposed have not proven satisfactory. They are not sufficiently hard or are too ductile or too elastic to properly take the strains transmitted through the core; or they do not closely overlie and conform to the core due to improper shrinkage or non-affinity for the core-piece. According to the present invention a suitable matrix material and a proper process of surrounding the core piece therewith have been discovered so that the resultant die is adequately backed, the matrix material being sufficiently hard, inelastic, non-ductile and non-brittle so that it will not readily split or permit the core piece to split and so closely and evenly overlying the core piece that no inequality of strain is permitted. Indeed, in the case Where a diamond core is used the matrix material is found to be so closely adherent to the core as apparently to form a union therewith.

The nature and objects of the invention will be better understood from an exposition of an exemplary and illustrative embodiment thereof when considered in connection with the accompanying drawing, wherein:

Fig. 1 is a cross-section of a die and holder, the view being taken on the line l--1 of Fig. 2;

Fig. 2 is a plan view thereof; and

Fig. 3 is a section through a mold assembly with the die in process of formation therein.

As shown in the drawing a hard core 10, for

example, a diamond, is encased in a matrix 11 0f the desired material. These elements forming the die proper are closely fitted into a holder 12 and if desired may be driven or welded therein. The assembly thus formed is in condition for mounting in a drawing machine so as to have wire or the like drawn therethrough in the direction of the arrow A in Fig. 1.

The matrix material at present preferred may have the following composition:

Per cent Iron 10 Nickel 15 Tungsten 30 Tungsten carbide But either iron or nickel may be used alone with the tungsten carbide, or the tungsten may be omitted, or the ratios of the various constituents may be varied. In some cases cobalt may be substituted for the iron or nickel or tungsten or all of them. In any case the composition formed will be extremely hard and tough andwill have good die-forming qualities of itself.

The die may be formed in a welding-carbon mold 15 disposed between water-cooled electrodes E1 and E2. The matrix material is preferably finely divided (say 300 mesh) tungsten carbide and metal which have been thoroughly mixed. The diamond or other core piece is held centered by projections 16 formed on the ends of carbon plugs 17 which also confine the matrix material about the core piece.

When thus assembled a considerable resilient pressure (say 1100 pounds per square inch) is imposed upon the carbon plugs 17 and electric current is turned on the electrodes. This sinters the matrix material and causes it to shrink in volume, the projections 16 of the carbon plugs 17 burning away or breaking down sufficiently to allow the plugs to follow up and maintain pressure upon the matrix material.

After sintering the pressure is left on the plugs while the die blank is allowed to cool between the water-cooled electrodes. It is an inherent fact that the matrix composed of these constituents and formed in this manner will be substantially free from voids, which is to say, that the voids, which are incident to sintering without pressure are so markedly reduced as to inake it proper to say that the material is substantially free from voids.

Upon cooling, the die blank thus produced is pierced through the core piece with the restricted portion of the pierced bore where the greatest drawing strains will be imposed located in the hard core piece. Normally the indentations in the blank left by the plug projections 16 serve to locate the line of piercing. The blank is then mounted in the holder 12 ready to be placed on a machine.

After the bore has become worn by use it may be re-bored for larger sizes and this may be repeated until the core is practically all used up to a thin outer shell. This benefit is attained in part because of the superior matrix material provided which is so hard and otherwise suitable that it may itself well serve for the flaring portions of the drawing bore.

Furthermore, with such a matrix, much smaller diamonds or other hard cores may be successfully used initially than with any known settings.

For example, where carat diamonds were formerly used for steel settings, and 1 carat diamonds for bronze settings, carat diamonds can by the present invention be used with equally good results; and likewise where 1 carat diamonds were required for steel settings and 4 carat diamonds for bronze settings, carat diamonds can now be used. The saving, it will be realized, will be much greater than is represented by the proportions in size because of the fact that diamonds and other gems are disproportionally cheaper in the smaller sizes.

Also the cost of manufacture is greatly reduced g by the present process.

By comparison, in a large shop it has been found that sixty (60) of the new die settings can be made in the time that was formerly required to make ten (10) by the old processes and materials. But above this is the fact that the dies made according to the present invention are practically all found by test to be free of faults while cast-metal set dies previously made were subject to many flaws and faults, most of which could not be readily detected. So that, not only the settings, but the much more valuable cores were frequently broken before they had given much service in the expected way.

In service the setting material is unaffected by high temperatures which formerly rendered useless dies having settings of other materials such as steel, bronze. etc.

The above description of the particular embodiment of the invention is illustrative merely and is not intended as defining the limits of the invention.

What I claim is: I

1. A drawing die comprising a .diamond core embedded in a matrix formed of a tungsten carbide composition which is substantially free from voids, the die being. pierced through the core to form the drawing bore and the restricted portion of the bore being located in the care.

2. A drawing die comprising a hard natural gem core embedded in a matrix formed of a tungsten carbide composition which is substantially free from voids, the die being'pierced through the core to form the drawing bore and the restricted portion of the bore being located in the core.

3. A drawing die comprising a hard natural gem core embedded in ar'natrix formed of a composition including tungsten carbide and a metal of the iron group. I

4. A drawing die comprising a hard natural gem core embedded in a matrix formed of a composition including tungsten carbide and a metal.

5. A drawing die comprising a hard natural gem core embedded in a matrix formed of a composition having approximately the composition,

iron 10%, nickel 15 tungsten 30%, and tungsten 

